Do not show shelf or top chrome hints while in Ash immersive mode

ash/common/material_design/material_design_controller.h

Index: ash/common/material_design/material_design_controller.h
diff --git a/ash/common/material_design/material_design_controller.h b/ash/common/material_design/material_design_controller.h
index c15b1ef49649c69b0865daed138193f89f9f0cb7..7df95833cffdf53eb30269960a06777f0d81dc73 100644
--- a/ash/common/material_design/material_design_controller.h
+++ b/ash/common/material_design/material_design_controller.h
@@ -43,6 +43,10 @@ class ASH_EXPORT MaterialDesignController {
   // Returns true if Material Design features are enabled for Chrome OS shelf.
   static bool IsShelfMaterial();
 
+  // Returns true if Material Design features are enabled for Chrome OS
+  // immersive mode.
+  static bool IsImmersiveModeMaterial();
+
   // Returns true if Material Design features are enabled for Chrome OS system
   // tray menu.
   static bool IsSystemTrayMenuMaterial();